There is general interest in developing commercially viable uses for agricultural by-products. Such by-products have the advantage of being abundant, renewable and relatively low cost sources of lignocellulosic raw materials. In addition, the production of large volumes of agricultural by-products may present a significant waste problem that raises both economic and environmental concerns. See Khalil et al. (2006) BioResources 1(2), 220-232.
Traditional methods of processing agricultural by-products and similar materials involve the use of acidic or alkaline chemical processes to break down or modify the fiber structure. Chemical methods for processing lignocellulosic biomass hydrolyze the polymers that make up their structure, wherein the choice of chemical process depends on the biomass structure and desired product. Most reactions used in the paper industry are alkaline in nature, such as the Kraft or sulfate process, which uses a solution of sodium sulfide and sodium hydroxide to digest the lignocellulosic material. Other methods based on the paper industry include soda (alkali) process, which involves digestion with 8% (w/w) sodium hydroxide solution to hydrolyze lignin at 170° C. and saturation pressure at this temperature.
In addition to generating undesirable waste streams, such processes are often complex, expensive, and require the use of specialized equipment and toxic or corrosive chemicals under controlled conditions. These traditional chemical processes are particularly dangerous and impracticable in many developing countries, which may lack the facilities and/or infrastructure to deal with these issues.
Agricultural by-products have been used for the production of various composite, textile, pulp and paper products. In addition, such materials have been explored for the production of fuel, as a source of chemicals, for the sequestration of heavy metals, and for other uses. For example, U.S. Pat. Nos. 6,027,652 and 6,506,307 describes a process for sorbing hydrophobic liquids, such as oil and gasoline, using tropical fibers. U.S. Pat. No. 5,958,182 describes a process for converting tropical materials into fibers useful in paper-making, textiles, insulation and other uses.
International Publication WO 95/25844 describes the preparation of high lignin content cellulosic fibers for use in absorbent structures by fluffing high lignin content fibers in air at elevated temperatures. U.S. Pat. No. 4,444,830 describes a process for preparing an absorbent fibrous hydrophilic fluff which contains absorbent polymer platelets distributed throughout the matrix, but does not describe the use of agricultural by-products. U.S. Pat. No. 6,059,924 describes a process for producing fluffed pulp having enhanced liquid wicking and retention by refining a chemical pulp slurry.
In the developing world, the agricultural by-products of many tropical plants represent an abundant and under-utilized source of lignocellulosic raw materials for a variety of applications. One potential use for such agricultural by-products is the production of water absorbent materials having a wide variety of useful applications. While natural fibers from trees and agricultural by-products are commonly available in many developing countries, the cellular structures of such natural fibers typically contain lignin, which is highly hydrophobic and is an obstacle to water absorption. Therefore, in their raw state, these natural fibers cannot be used to produce water absorbent materials.
One potential use for such water absorbent materials is the production of absorbent articles, such as fiber pads, sanitary pads and the like. Lack of access to affordable sanitary pads is a major barrier to education and employment in many developing countries, where millions of women and girls miss up to 50 days of school or work per year when they menstruate. Frequently, foreign-produced brands of sanitary pads are often too costly for these women and girls to obtain. For example, in Rwanda, 36% of girls who miss school do so because they do not have access to affordable sanitary pads. Alternatively, some women in developing countries resort to using rags, which are unhygienic, ineffective and potentially harmful.
Thus, there remains a need for a simple and inexpensive method of producing absorbent articles, using abundant natural fibers from agricultural by-products. The development of non-chemical processes to utilize these agricultural by-products would be especially desirable.